What is it
Newton's three laws of motion describe how forces affect movement: an object stays at rest or constant velocity unless acted on by a force, force equals mass times acceleration (F = ma), and every action has an equal and opposite reaction.
Why it matters
Newton's second law (F = ma) is the single equation that connects forces to motion, making it the mathematical engine behind almost every mechanics problem you'll ever solve, from simple blocks to complex systems.
Exam tip
When applying F = ma to connected objects (like two masses joined by a string), treat each object with its own separate equation before combining them — trying to apply one equation to the whole system at once is where most connected-particle errors occur.
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